Since you pulled the distributor, see if there's any play in it causing the reluctor contacts to hit in a few places. If they do, then you'll either want to rebuild that distributor or replace it. It might just be easier to replace it. BUT, that's only if there's play in the shaft from side to side. You should be able to look at the contact points and see if any are worn more so than others. Some sensors won't always throw a code for some reason. It could very well be the CTS. I don't know if that's been problematic with many GM products, but I do know that Saturns are notorious for that.
1994 Chevy Surburban running way too rich and ...
- Thread starter T-Max
- Start date
Chuzz -
Thanks again for your feedback. I note that Saturn Corp. is a subsidiary of Chevrolet.
I'm still working on the problem but didn't get to work on it yesterday or today. The distributor was fine; there was no play to speak of and no indication of play in the cap (like worn contacts). All contacts appeared normal and I cleaned them up a bit. I put it back in on Saturday and had no problem starting the truck. But I do need to re-set the timing. I located the "EST bypass wire" (brown wire with black stripe) and its connector under the dash near the heater blower, so I can disconnet that when I set the timing.
Today I bought a new fuel filter, PCV valve and coolant temperature sensor (CTS). I'll put the fuel filter on first and see if that results in any change. I assume it could stand a new fuel fiter in any event. I'll also put the new PCV valve on (it likely needs that too). As to the CTS, I plan to disconnect the wire on the old one and start the truck and see if the disconnected wire sets an error code. As to the new one, I think I don't need to actually install it to "try it out." I think I can just plug in the wire connector and make sure the base is grounded (as if it were screwed in) and that should suffice to show whether or not it makes any difference when I start the truck. The truck will be cold when I do this so whether or not it's actually screwed in shouldn't make any difference. It would be cold if screwed in and it'll be cold when not screwed in. As long as it's grounded, I can't see it making any difference.
If it doesn't make any difference I can take it back. I may or may not do that. I might put it in anyway. Or I might take it back and exchange it for an O2 sensor.
But if I do want to take it back, it'll be easy because it's not packed in plastic (like everything else seems to be today) It just comes in a small box (surprisingly). So they won't even know that I "opened" it (not that they care).
So that's the current status.
You hit that nail on the head.
Indeed it was the CTS. And indeed it did not set a code.
First thing I did today was to pull a plug from each side to see what they looked like. They were seriously carboned up (lots of black soot)
I had driven it on Sunday for a 15 mile highway ride home and it was running pretty crappy but I was hoping that the highway trip would produce better looking plugs.
but not so
So then I wiped them clean and put 'em back in and tried to start it and it wouldn't hardly start. When it did start, it wouldn't stay running at idle.
So I decided to pull the wire connector off the CTS and see if that set a code for it. I started it with the wire connector off the CTS and son-of-a-gun if it didn't start right up and run like it should. Easy peasy.
cool !!
And it did set a 15 code (coolant sensor circuit low or open)
So I put the new one in, cleared the codes from the 'puter, and it's running like it should.
It's still missing a little bit now and then. I assume that's because the other 6 plugs are still sooty and need to burn themselves clean over time. If need be, I'll pull some other plugs later on and see how they look. They are relatively new plugs with not a lot of miles on them cuz I hardly drive this thing unless I absolutely have to.
I also put the new PCV valve on and will put the fuel filter on when I get a minute
So that's what it wuz. Now I need to re-set the timing and that's going to be a PITA because I frankly don't know how I'm going to be able to see the timing mark like I need to. There's too much other stuff in the way, as best I can tell. I believe I see the plate that has the timing marks on it, and I KNOW I've identified the timing mark on the crank pulley, but if I'm correct about the plate, it's really in an impossible place to see from the proper angle for setting the timing.
Just one more thing I guess.
Anyway, at least the weather's nice and the main problem is solved.
I looked more closely at the timing "plate" and see that I can, indeed, see the timing mark without any problem. And there is already a spot of yellow paint on both the plate and the timing mark on the crank hub. So I'm all set.
I went to time it and found that my timing light isn't working, so I need to address that and then I'll be all set.
Thanks again to you and Chuzz for your input. As I said before, the one guy on YouTube said that the CTS is the most likely sensor to fail and is almost always the problem. And he was right.
There's no more "too rich" smell at the tailpipe and I'm really looking forward to seeing that puppy turn from black to a nice charcoal gray.
Glad to hear that you're up and running almost normally, TJ. Drive it hard a couple of times after it warms up and that may help burn the soot off the plugs. Get the timing set and I'm pretty sure you'll be okay. Post back if not and I'll try to come up with some other outlandish stuff to try. LOL And a note to Cside, the CTS is your coolant temperature sensor.
I looked more closely at the timing "plate" and see that I can, indeed, see the timing mark without any problem. And there is already a spot of yellow paint on both the plate and the timing mark on the crank hub. So I'm all set. I went to time it and found that my timing light isn't working, so I need to address that and then I'll be all set. There's no more "too rich" smell at the tailpipe and I'm really looking forward to seeing that puppy turn from black to a nice charcoal gray.
Just to follow up on my situation, I've now timed the truck to the painted mark on the "sawtooth scale plate." That mark was put there by the former owner's mechanic. I can't confirm that the mark is actually on TDC ("O") because the plate is too far away from me (I can't get close enough to it) and it's too dirty and/or rusty to read the marks on it.
My timing light (which I haven't used in years) didn't work, so I borrowed an ancient neon timing light from my elderly neighbor and used that. Because the neon light is so faint and didn't show the crankshaft mark very clearly at all, it ended up taking me quite a long time to confirm that mark on the spinning crankshaft. But I finally was able to accomplish that.
Before I started, I pulled the #4 plug (easy to get to). Despite the fact that I've only driven the truck ~ 5 miles (on two separate trips), plus idling it quite a bit during the timing effort, that plug was EXTREMELY clean. So just that bit of running the engine (which never really warmed up fully) was enough to burn that formerly black and sooty plug clean. Very impressive indeed. It's amazing how much better the truck runs now and I can't wait to take it out on the highway and give it a good road test.
As to the timing, I think it's advanced more than it should be. On the other hand, it's likely set to where it's been for as long as I've owned the truck (7 years now) since I've never before changed the timing. And it's always run quite well whenever it wasn't running poorly, which it has been (off and on) for quite some time now, likely due to the bad CTS which has probably been going bad for awhile. The truck has (in my view) been running at least a bit too rich for the past several years. Now that I see how clean-burning the #4 plug is now, I'm confident that it HAS been running a bit too rich, as I suspected. When the CTS finally completely failed recently, then it began running WAY too rich and forced me to find the problem.
BTW, I don't use this truck much at all, so the fact that's it hasn't been running "optimally" hasn't mattered all that much.
Now, as to why I think the current setting may be a bit too advanced, see what you think about what I did. I removed the distributor cap (and all of its spark plug wires) and manually aligned the timing marks (the yellow painted marks made by the former owner's mechanic). The engine can be manually turned over to make the final alignment using a suitably long breaker bar (for leverage) and a 5/8" socket on the crank pully bolt. Then I eyed the rotor position with one of the tall bolts that hold the air cleaner on and placed a mark on the firewall so that when I sighted along the line of the tall bolt with that mark, the rotor was pointing right at the bolt.
Then I put the distributor cap back on and sighted along the line. The #1 "stud" on the cap (on which the #1 spark plug wire sits) should have also been lined up with my line if the distributor is indeed set to TDC. But it wasn't. It was quite a bit to the right of that line. Which means that it was in a somewhat advanced position. And it's still in that position because that's where the marks line up with the timing light.
Now, I know this is not exactly a precise indication of things, but it really makes me wonder whether or not the mechanic put that painted mark @ "O". He may have put it at 4 degrees advanced, or ..... ??
So the last thing I want to do is to somehow determine exactly where that mark is, which doesn't look like it's going to be very easy, and re-adjust the timing if necessary.
I've searched online for a picture of the "sawtooth scale plate" on this 1994 truck but haven't found one that shows this actual plate.
So I guess I'll have to endeavor to clean my plate and somehow get a gander at the markings so's I can see what the deal is with the current painted mark.
I really don't want to run the truck with the spark advanced beyond TDC (as called for) unless it's really required, performance-wise. Which I doubt is the case.
The thing's got 197,000 miles on it and it's not such a good idea to run an older high-mileage motor with the spark advanced.
In any event, the moral of my story is that if you find your 5.7 liter TBI is perhaps running a bit too rich and not as clean-burning as you think it should be, ya might want to invest in a new CTS for under 20 bucks. Because I suspect that I've been driving mine with a somewhat defective CTS for quite some time.
In my case, I also replaced the fuel pressure regulator (which is also an easy fix) for $59.00. I had to because mine was leaking. That might (or might not) have also been contributing to the too rich air/fuel mix.
But for now, everything seems to be all good, and probably better than it's been in quite awhile.